1. Field of the Invention
This invention relates to an apparatus for forming a reactive deposition film such as a cubic boron nitride film on a part, a tool or the like which requires wear resistance and corrosion resistance.
2. Description of the Prior Art
Methods disclosed in the Japanese Patent Opening Gazette Nos. 204370/1986, 47472/1987 and 77454/1987 are given as examples for the forming techniques of the cubic boron nitride film by the reactive vapor deposition.
In the method disclosed in the Japanese Patent Opening Gazette No. 204370/1986, plasma abundant in electrons is produced by hollow cathode discharge, and a part of the electrons are attracted towards a reaction gas inlet. Gas is activated, and so reactivity for reactive vapor deposition has been improved.
In the method disclosed in the Japanese Patent Opening Gazette No. 47472/1987, a DC or AC bias voltage is applied to a reaction gas introducing nozzle which is called "activation nozzle", so that plasma is produced with high density. Ions are injected to a body to be coated, from the plasma of high density. Radio frequency (rf) or high frequency bias voltage is applied to the body to be coated. Thus, a cubic boron nitride film is formed on the body.
In the Japanese Patent Opening Gazette No. 77454/1987, such a method for forming a cubic boron nitride film is disclosed that a DC or AC bias voltage is applied to the activation nozzle to produce a plasma of high density, a rf bias voltage is applied to a body to be coated, and a reaction gas such as nitrogen gas or hydronitrogen gas and a discharge base gas such as argon are mixed and introduced into the vacuum chamber through the activation nozzle, or concurrently introduced thereinto.
In both of the above described second method (Japanese Patent Opening Gazette No. 47472/1987) and third method (Japanese Patent Opening Gazette No. 77454/1987), the bias voltage is applied to the gas introducing nozzle so that plasma of high density is produced adjacent to the opened portion of the gas introducing nozzle, while the rf bias voltage is applied to the body to be coated, and ions are injected into the body from the plasma of high density so as to form a cubic boron nitride film on the body.
The cubic boron nitride film can be formed on the body such as the part or the tool by the above-described methods in which the activation nozzle is provided, and the rf bias voltage is applied to the body to be coated. However, the plasma density is low in a region adjacent to some portion of the body being farther from the activation nozzle. Accordingly, the area on which the cubic boron nitride film can be formed, cannot be increased in the body to be coated. When the above described methods are used for an actual manufacturing apparatus, the number of the activation nozzles should be increased for forming the cubic boron nitride film on a sufficiently wide area of the body. The cost and size of the actual manufacturing apparatus become accordingly high and large.